1. Field of the Invention
This invention relates to a new process for the production of optionally foamed moldings based on polyurethanes and/or polyureas having a compact surface and outstanding mold-release properties by the reaction in closed molds of an optionally foamable reaction mixture of polyisocyanates, compounds containing isocyanate-reactive hydrogen atoms and internal mold release agents based on certain salts of organic carboxylic acids and tertiary amines.
2. Description of the Prior Art
The molds used in the production of polyurethane- and/or polyurea-based moldings are preferably made of metal. In order during mold release to prevent the molding from adhering to the surface of the mold, the mold is frequently coated with an external release agent. However, it is also known that the effect of external release agents can be improved or their use rendered largely superfluous by also using so-called internal release agents.
Thus, it is disclosed in DE-OS No. 1,953,637 that the need to apply an external mold release agent may be eliminated by adding to the foamable reaction mixture certain additives which impart excellent release properties to the finished molding in metal molds. Salts of aliphatic carboxylic acids containing at least 25 carbon atoms with preferably primary amines or amines containing amide or ester groups are recommended for use as these additives.
DE-OS No. 2,121,670 recommends the use of binary or ternary mixtures of different internal mold release agents, salts of aliphatic carboxylic acids containing at least 20 carbon atoms with amines optionally containing amide and/or ester groups being suitable for use as one of the components of these mixtures.
DE-OS No. 2,431,968 recommends certain salts of saturated or unsaturated aliphatic or cycloaliphatic carboxylic acids containing at least 8 carbon atoms and tertiary amines which do not contain any amide or ester groups and in which the atomic ratio of tertiary amine nitrogen to carbon in the amine molecule is 1:3 to 1:12 for use as internal mold release agents.
In the continuing search for internal release agents which provide a good release effect, it has now been found that salts of saturated or unsaturated aliphatic or cycloaliphatic carboxylic acids containing at least 8 carbon atoms and tertiary amines substituted by a hydrocarbon radical containing at least 12 carbon atoms are particularly effective internal mold release agents. The release agents suitable for use in accordance with the invention which are described in detail hereinafter are distinguished from the release agents preferably used in accordance with DE-OS No. 2,431,968 in particular by the fact that the catalytic effect of the tertiary amines present in protonized form in the salts is of subsidiary importance so that the use of the release agents according to the invention does not have any significant effect on the reactivity of the reaction mixtures.